sa1012.go raw

   1  package sa1012
   2  
   3  import (
   4  	"go/ast"
   5  	"go/types"
   6  
   7  	"honnef.co/go/tools/analysis/code"
   8  	"honnef.co/go/tools/analysis/edit"
   9  	"honnef.co/go/tools/analysis/lint"
  10  	"honnef.co/go/tools/analysis/report"
  11  	"honnef.co/go/tools/go/types/typeutil"
  12  	"honnef.co/go/tools/pattern"
  13  
  14  	"golang.org/x/tools/go/analysis"
  15  	"golang.org/x/tools/go/analysis/passes/inspect"
  16  )
  17  
  18  var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
  19  	Analyzer: &analysis.Analyzer{
  20  		Name:     "SA1012",
  21  		Run:      run,
  22  		Requires: []*analysis.Analyzer{inspect.Analyzer},
  23  	},
  24  	Doc: &lint.RawDocumentation{
  25  		Title:    `A nil \'context.Context\' is being passed to a function, consider using \'context.TODO\' instead`,
  26  		Since:    "2017.1",
  27  		Severity: lint.SeverityWarning,
  28  		MergeIf:  lint.MergeIfAny,
  29  	},
  30  })
  31  
  32  var Analyzer = SCAnalyzer.Analyzer
  33  
  34  var checkNilContextQ = pattern.MustParse(`(CallExpr fun@(Symbol _) (Builtin "nil"):_)`)
  35  
  36  func run(pass *analysis.Pass) (interface{}, error) {
  37  	todo := &ast.CallExpr{
  38  		Fun: edit.Selector("context", "TODO"),
  39  	}
  40  	bg := &ast.CallExpr{
  41  		Fun: edit.Selector("context", "Background"),
  42  	}
  43  	fn := func(node ast.Node) {
  44  		m, ok := code.Match(pass, checkNilContextQ, node)
  45  		if !ok {
  46  			return
  47  		}
  48  
  49  		call := node.(*ast.CallExpr)
  50  		fun, ok := m.State["fun"].(*types.Func)
  51  		if !ok {
  52  			// it might also be a builtin
  53  			return
  54  		}
  55  		sig := fun.Type().(*types.Signature)
  56  		if sig.Params().Len() == 0 {
  57  			// Our CallExpr might've matched a method expression, like
  58  			// (*T).Foo(nil) – here, nil isn't the first argument of
  59  			// the Foo method, but the method receiver.
  60  			return
  61  		}
  62  		if !typeutil.IsTypeWithName(sig.Params().At(0).Type(), "context.Context") {
  63  			return
  64  		}
  65  		report.Report(pass, call.Args[0],
  66  			"do not pass a nil Context, even if a function permits it; pass context.TODO if you are unsure about which Context to use", report.Fixes(
  67  				edit.Fix("use context.TODO", edit.ReplaceWithNode(pass.Fset, call.Args[0], todo)),
  68  				edit.Fix("use context.Background", edit.ReplaceWithNode(pass.Fset, call.Args[0], bg))))
  69  	}
  70  	code.Preorder(pass, fn, (*ast.CallExpr)(nil))
  71  	return nil, nil
  72  }
  73